Battery-operated devices, such as mobile telephones and other hand-held devices, include increasing numbers of voltage regulators for supplying power to different functions such as radio frequency transceivers, base band circuits, audio circuits, liquid crystal displays, multi-media cards, Bluetooth communication circuits, universal serial bus (‘USB’) circuits, and vibrators for example. Each voltage regulator passes a quiescent current and the multiplication of voltage regulators multiplies the overall wastage of battery power due to the quiescent currents, reducing battery autonomy between recharging operations.
FIG. 1 of the accompanying drawings shows a voltage regulator 100 connected between a supply rail 102 and ground 104, between which a battery 106 is connected to supply power. the voltage regulator 100 provides a regulated output voltage Vout at an output node 108 to which a load 110 can be connected to receive a supply current i_load. The quiescent current icq of the regulator flows in parallel with the load current i_load and the battery 106 is drained by the sum of the currents i_load+icq. The quiescent current has a larger impact in proportion during low power or standby operation, when the load current i_load is small, which often lasts for longer periods than high power operation.
It is possible to include additional circuits in the regulator to reduce quiescent current automatically during low power or standby operation without reducing the performance of the high power operation. FIG. 2 of the accompanying drawings shows a multimode voltage regulator 200 comprising a high power voltage regulator module 202, a low power voltage regulator module 204 and a multimode control module 206 for causing either the high power voltage regulator module 202 or the low power voltage regulator module 204 to supply the load. In a variant of this circuit, during operation in the high power mode, both the high power voltage regulator module 202 and the low power voltage regulator module 204 supply the load.
US patent specification 2003/0178976 discloses a multimode voltage regulator in which a control module varies biasing for a low power voltage regulator module and a high power voltage regulator module to control the operational mode between a normal operation mode and a SLEEP mode.